JP2008016821A - Reflective mask blank for euv lithography and substrate with functional film for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an EUV mask blank in which reduction of reflectivity during an EUV exposure is suppressed, and also to provide a substrate with a functional film to be employed for fabricating the EUV mask blank. <P>SOLUTION: The substrate with a reflective layer for EUV lithography has, on a substrate, a reflective layer which reflects an EUV light, and a protective layer for protecting the reflective layer formed in this order, and is characterized in that the protective layer contains, as a component, ruthenium (Ru) and at least one selected from the group consisting of boron (B), and zirconium (Zr) with the content percentage of Ru ranging from 70 at% to 95 at% and a total of the content percentages of B and Zr ranging from 5 at% to 30 at% in the protective layer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reflective mask blank (hereinafter referred to as “EUV mask blank”) for EUV (Extreme Ultraviolet) lithography used in semiconductor manufacturing and the like, and the production of the EUV mask blank. The present invention relates to a functional film-coated substrate and an EUV mask obtained by patterning the EUV mask blank.

  2. Description of the Related Art Conventionally, in the semiconductor industry, a photolithography method using visible light or ultraviolet light has been used as a technique for transferring a fine pattern necessary for forming an integrated circuit having a fine pattern on a silicon substrate or the like. However, while miniaturization of semiconductor devices is accelerating, the limits of conventional photolithography methods have been approached. In the case of the photolithography method, the resolution limit of the pattern is about ½ of the exposure wavelength, and it is said that the immersion wavelength is about ¼ of the exposure wavelength, and the immersion of ArF laser (193 nm) is used. Even if the method is used, the limit of about 45 nm is expected. Therefore, EUV lithography, which is an exposure technique using EUV light having a wavelength shorter than that of an ArF laser, is promising as an exposure technique for 45 nm and beyond. In this specification, EUV light refers to light having a wavelength in the soft X-ray region or vacuum ultraviolet region, and specifically refers to light having a wavelength of about 10 to 20 nm, particularly about 13.5 nm ± 0.3 nm.

  Since EUV light is easily absorbed by any material and the refractive index of the material is close to 1 at this wavelength, a conventional refractive optical system such as photolithography using visible light or ultraviolet light may be used. Can not. For this reason, in the EUV light lithography, a reflective optical system, that is, a reflective photomask and a mirror are used.

The mask blank is a laminated body before patterning used for photomask manufacturing. In the case of an EUV mask blank, a reflective layer that reflects EUV light and an absorber layer that absorbs EUV light are formed in this order on a glass substrate or the like. As the reflective layer, a molybdenum (Mo) layer, which is a high refractive layer, and a silicon (Si) layer, which is a low refractive layer, are alternately laminated, thereby increasing the light reflectance when EUV light is irradiated on the surface of the layer. A multilayer reflective film is usually used.
For the absorber layer, a material having a high absorption coefficient for EUV light, specifically, a material mainly composed of chromium (Cr) or tantalum (Ta) is used.

A protective layer is usually formed between the reflective layer and the absorber layer to prevent oxidation of the reflective layer surface. Conventionally, Si has been widely used as a material for the protective layer. On the other hand, Patent Document 1 proposes the use of ruthenium (Ru) as a protective layer material.
When Ru is used as the material of the protective layer, a high etching selectivity with respect to the absorber layer can be obtained, and a high reflectance can be obtained as compared with the case where the Si film is used as the protective layer. However, when Ru is used as the material for the protective layer, it diffuses between the Ru protective layer and the outermost Si layer of the multilayer reflective film during the heating process (for example, resist baking process) during mask manufacturing or EUV exposure. Since the layer is formed and the diffusion layer is oxidized, there is a problem that the reflectance of the reflective layer is lowered.
In particular, since the decrease in reflectance during EUV exposure proceeds with time, it is necessary to change the exposure conditions in the middle, and the life of the mask is shortened.

In order to solve such a problem, Patent Document 2 discloses a ruthenium compound containing Ru and at least one selected from Mo, Nb, Zr, Y, B, Ti, and La (Ru content of 10 to 95 at). %) Has been proposed.
In the case of this protective layer, it is described that it is possible to suppress diffusion layer formation between the protective layer made of a ruthenium compound and the Si layer on the surface of the multilayer reflective film in the heating process (resist baking) at the time of manufacturing the mask. Has been.

JP 2002-122981 A JP 2005-268750 A

However, in the case of the protective layer described in Patent Document 2, it is not clear whether there is an effect of suppressing a decrease in reflectivity during EUV exposure, and further, elements such as Mo contained in the ruthenium compound are more etched than Ru. Therefore, when the content of these elements is large, there is a problem that the etching characteristics as a protective layer are deteriorated.
The present invention provides an EUV mask blank in which a decrease in reflectance during EUV exposure is suppressed, and a substrate with a functional film used for manufacturing the EUV mask blank, in order to solve the above-described problems of the prior art. With the goal.

As a result of intensive studies to solve the above problems, the present inventors have made amorphous the crystal structure of the protective layer containing Ru as a material, thereby allowing diffusion between the protective layer and the Si layer on the surface of the multilayer reflective film. It has been found that layer formation can be suppressed and a decrease in reflectance during EUV exposure can be suppressed.
In order to make the crystal structure of the protective layer amorphous, the present inventors set the components of the protective layer as Ru and at least one selected from the group consisting of boron (B) and zirconium (Zr). And it discovered that it was effective to make the ratio of each component into a specific range.

The present invention has been made based on the above-mentioned findings of the present inventors, and an EUV in which a reflective layer that reflects EUV light and a protective layer that protects the reflective layer are formed on a substrate in this order. A substrate with a reflective layer for lithography,
The protective layer contains ruthenium (Ru) and at least one selected from the group consisting of boron (B) and zirconium (Zr) as components,
There is provided a substrate with a reflective layer for EUV lithography, wherein the protective layer has a Ru content of 70 at% to 95 at% and a total content of B and Zr of 5 at% to 30 at%.

Further, the present invention is a substrate with a reflective layer for EUV lithography, wherein a reflective layer for reflecting EUV light and a protective layer for protecting the reflective layer are formed in this order on the substrate,
The protective layer contains Ru and at least one selected from the group consisting of B and Zr as components.
The total content of B and Zr in the protective layer is such that the total content of B and Zr on the reflective layer side is high and the total content of B and Zr on the surface side is low. A gradient composition film that varies along the thickness direction of the layer,
The total content of B and Zr on the reflective layer side is 5 at% to 30 at%,
Provided is a substrate with a reflective layer for EUV lithography, wherein the total content of B and Zr on the surface side is 0 at% to 20 at%.

  Hereinafter, in this specification, the substrates with a reflective layer for EUV lithography described in [0010] and [0011] are collectively referred to as “the substrate with a reflective layer of the present invention”.

  In the substrate with a reflective layer of the present invention, it is preferable that the crystal state of the protective layer is amorphous.

Further, the present invention is a substrate with a reflective layer for EUV lithography, wherein a reflective layer for reflecting EUV light and a protective layer for protecting the reflective layer are formed in this order on the substrate,
The protective layer contains ruthenium (Ru) and at least one element selected from the group consisting of boron (B) and zirconium (Zr) as components,
The content of Ru in the protective layer is 70 at% to 95 at%, the total content of B and Zr is 5 at% to 30 at%,
There is provided a substrate with a reflective layer for EUV lithography, wherein the protective layer has an amorphous crystal structure.

Further, the present invention is a substrate with a reflective layer for EUV lithography, wherein a reflective layer for reflecting EUV light and a protective layer for protecting the reflective layer are formed in this order on the substrate,
The protective layer contains Ru and at least one element selected from the group consisting of B and Zr,
The total content of B and Zr in the protective layer is such that the total content of B and Zr on the reflective layer side is high and the total content of B and Zr on the surface side is low. A gradient composition film that varies along the thickness direction of the layer,
The total content of B and Zr on the reflective layer side is 5 at% to 30 at%,
The total content of B and Zr on the surface side is 0 at% to 20 at%,
There is provided a substrate with a reflective layer for EUV lithography, wherein the protective layer has an amorphous crystal structure.

  Hereinafter, in this specification, the substrate with a reflective layer for EUV lithography described in [0014] and [0015] is also collectively referred to as “the substrate with a reflective layer of the present invention”.

In the substrate with a reflective layer of the present invention, the protective layer is preferably made of any of the following solid solutions.
Solid solution of Ru and B Solid solution of Ru and Zr Solid solution of Ru, B and Zr

  In the substrate with a reflective layer of the present invention, when the protective layer contains Ru and B as components, it is preferable that the crystal state of the protective layer is kept amorphous up to 200 ° C. in vacuum (1 Pa or less).

  In the substrate with a reflective layer of the present invention, when the protective layer contains Ru and Zr, the crystalline state of the protective layer is preferably maintained in an amorphous state up to 400 ° C. in vacuum (1 Pa or less). .

  In the substrate with a reflective layer of the present invention, the surface roughness of the protective layer surface is preferably 0.5 nm rms or less.

  In the substrate with a reflective layer of the present invention, the protective layer preferably has a thickness of 1 to 10 nm.

  The present invention also provides a reflective mask blank for EUV lithography (hereinafter also referred to as “the EUV mask blank of the present invention”) formed by forming an absorber layer on the protective layer of the substrate with a reflective layer of the present invention. I will provide a.

  In the EUV mask blank of the present invention, the absorber layer is preferably formed of a material mainly composed of tantalum (Ta).

  In the EUV mask blank of the present invention, it is preferable that the etching selectivity between the protective layer and the absorber layer is 10 or more when plasma etching is used.

  In the EUV mask blank of the present invention, a low reflection layer for inspection light used for inspection of a mask pattern, which is formed of a material mainly containing tantalum (Ta), is provided on the absorber layer. preferable.

  In the case where a low reflection layer is formed on the absorber layer, the reflected light on the surface of the protective layer with respect to the wavelength of light used for inspection of the pattern formed on the absorber layer, and the surface on the surface of the low reflection layer The contrast with the reflected light is preferably 30% or more.

  The present invention also provides a reflective mask for EUV lithography (hereinafter also referred to as “the EUV mask of the present invention”) obtained by patterning the EUV mask blank of the present invention.

In the substrate with a reflective layer of the present invention, formation of a diffusion layer between the protective layer and the Si layer on the surface of the multilayer reflective film can be suppressed during the formation of the protective layer. Thereby, the reflectance fall by diffusion layer formation is suppressed.
In the EUV mask blank of the present invention, formation of a diffusion layer between the protective layer and the Si layer on the surface of the multilayer reflective film can be suppressed during heat treatment such as resist baking. Thereby, the reflectance fall by diffusion layer formation is suppressed.
In the EUV mask of the present invention, formation of a diffusion layer between the protective layer and the Si layer on the surface of the multilayer reflective film can be suppressed during EUV exposure. Thereby, the reflectance fall by diffusion layer formation is suppressed. Therefore, the EUV mask of the present invention is a highly reliable EUV mask with little change in reflectance over time.

Hereinafter, the EUV mask blank of the present invention will be described with reference to the drawings.
FIG. 1 is a schematic cross-sectional view showing an embodiment of the EUV mask blank of the present invention. A mask blank 1 shown in FIG. 1 includes a reflective layer 12 that reflects EUV light on a substrate 11 and a protective layer 13 that protects the reflective layer 12 in this order. An absorber layer 14 is formed on the protective layer 13.
Hereinafter, individual components of the mask blank 1 will be described.

The substrate 11 is required to satisfy the characteristics as a substrate for an EUV mask blank. Therefore, the substrate 11 preferably has a low thermal expansion coefficient (0 ± 1.0 × 10 ⁻⁷ / ° C., more preferably 0 ± 0.3 × 10 ⁻⁷ / ° C., and further preferably 0 ± 0.2. × 10 ⁻⁷ / ° C., more preferably 0 ± 0.1 × 10 ⁻⁷ / ° C., particularly preferably 0 ± 0.05 × 10 ⁻⁷ / ° C.), smoothness, flatness, and mask blank Or the thing excellent in the tolerance to the washing | cleaning liquid used for the washing | cleaning etc. of the photomask after pattern formation is preferable. Specifically, the substrate 11 is made of glass having a low thermal expansion coefficient, such as SiO ₂ —TiO ₂ glass, but is not limited thereto, and is not limited to crystallized glass, quartz glass, silicon, A substrate made of metal or the like can also be used. A film such as a stress correction film may be formed on the substrate 11.
The substrate 11 preferably has a smooth surface of 0.15 nm rms or less and a flatness of 100 nm or less in order to obtain high reflectance and transfer accuracy in a photomask after pattern formation.
The size, thickness, etc. of the substrate 11 are appropriately determined by the design value of the mask. In the examples described later, SiO ₂ —TiO ₂ glass having an outer shape of 6 inches (152.4 mm) square and a thickness of 0.25 inches (6.3 mm) was used.
It is preferable that the surface of the substrate 11 on the side where the reflective layer 12 is formed has no defects. However, even if it exists, the depth of the concave defect and the height of the convex defect are not more than 2 nm so that the phase defect does not occur due to the concave defect and / or the convex defect. It is preferable that the half width of the defect and the convex defect is 60 nm or less.

  The reflective layer 12 is not particularly limited as long as it has desired characteristics as a reflective layer of an EUV mask blank. Here, the characteristic particularly required for the reflective layer 12 is a high EUV light reflectance. Specifically, when the surface of the reflective layer 12 is irradiated with light in the wavelength region of EUV light at an incident angle of 6 degrees, the maximum value of light reflectance near a wavelength of 13.5 nm is preferably 60% or more, More preferably, it is 65% or more. Even when the protective layer 13 is provided on the reflective layer 12, the maximum value of the light reflectance near the wavelength of 13.5 nm is preferably 60% or more, and more preferably 65% or more. preferable.

  Since the reflective layer 12 can achieve high EUV light reflectance, a multilayer reflective film in which a high refractive layer and a low refractive index layer are alternately laminated a plurality of times is usually used as the reflective layer 12. In the multilayer reflective film forming the reflective layer 12, Mo is widely used for the high refractive index layer, and Si is widely used for the low refractive index layer. That is, the Mo / Si multilayer reflective film is the most common. However, the multilayer reflective film is not limited to this, and for example, a Mo compound / Si compound multilayer reflective film can also be used.

  The film thickness of each layer constituting the multilayer reflective film constituting the reflective layer 12 and the number of repeating units of the layers can be appropriately selected according to the film material used and the EUV light reflectance required for the reflective layer. Taking the Mo / Si reflective film as an example, in order to obtain the reflective layer 12 having a maximum EUV light reflectance of 60% or more, the multilayer reflective film is composed of a Mo layer having a film thickness of 2.3 ± 0.1 nm, A Si layer having a thickness of 4.5 ± 0.1 nm may be laminated so that the number of repeating units is 30 to 60.

In addition, what is necessary is just to form each layer which comprises the multilayer reflective film which comprises the reflective layer 12 so that it may become desired thickness using well-known film-forming methods, such as a magnetron sputtering method and an ion beam sputtering method. For example, when an Si / Mo multilayer reflective film is formed by ion beam sputtering, an Si target is used as a target, and Ar gas (gas pressure 1.3 × 10 ⁻² Pa to 2.7 × 10 ⁻ is used as a sputtering gas. ² Pa), an Si film is formed to have a thickness of 4.5 nm at an ion acceleration voltage of 300 to 1500 V and a film formation rate of 0.03 to 0.30 nm / sec. using a target, using an Ar gas (gas pressure ^{1.3 × 10 -2 Pa~2.7 × 10 -2} Pa), an ion acceleration voltage 300 to 1,500 V, the deposition rate of 0.03 to 0 It is preferable to form the Mo film so that the thickness is 2.3 nm at 30 nm / sec. With this as one period, the Si / Mo multilayer reflective film is formed by laminating the Si film and the Mo film for 40 to 50 periods.

The protective layer 13 is used to protect the reflective layer 12 from being damaged by the etching process when the absorber layer 14 is patterned by an etching process, usually a plasma etching process, and the surface of the reflective layer 12. Is provided for the purpose of preventing oxidation. Note that the protective layer 13 itself preferably has a high EUV light reflectance so that the EUV light reflectance in the reflective layer 12 is not impaired even after the protective layer 13 is formed.
In the EUV mask blank 1 of the present invention, the protective layer 13 is composed of ruthenium (Ru) and at least one selected from the group consisting of boron (B) and zirconium (Zr), and the ratio of these components is This is a specific range described later. In the protective layer 13, Ru and at least one selected from the group consisting of B and Zr form one of the following solid solutions. Here, the solid solution means that two or more kinds of elements are dissolved in each other and the whole is a uniform solid phase, and does not include an intermetallic compound having a crystal lattice.
・ Solid solution of Ru and B (Solid solution (A))
・ Solid solution of Ru and Zr (solid solution (B))
-Solid solution of Ru, B and Zr (solid solution (C))

In the protective layer 13, that is, in the above solid solution, when the Ru content is 70 at% to 95 at% and the total content of B and Zr is 5 at% to 30 at%, Ru, B Since Zr is difficult to form a compound having a crystal lattice, it is preferable that the crystal state of the protective layer 13 easily becomes amorphous. Therefore, in the case of the solid solution (A), it is preferable that the Ru content is 70 at% to 95 at% and the B content is 5 at% to 30 at% because the crystalline state of the protective layer 13 is likely to be amorphous. In the case of the solid solution (B), it is preferable that the Ru content is 70 at% to 95 at% and the Zr content is 5 at% to 30 at% because the crystal state of the protective layer 13 tends to be amorphous. In the case of the solid solution (C), it is preferable that the Ru content is 70 at% to 95 at% and the total content of B and Zr is 5 at% to 30 at% because the crystalline state of the protective layer 13 tends to be amorphous.
The protective layer 13 may contain elements other than Ru, B and Zr as long as the technical effect as the protective layer is exhibited.

In the solid solutions (A) to (B), the reason why the crystalline state of the protective layer 13 becomes amorphous when Ru, B, and Zr are set to the above-described contents can be considered as follows.
Since the volume difference (atomic radius difference) of atoms contained in the solid solution is large, it is considered that the crystal state of the protective layer 13 (solid solution) is likely to be amorphous when Ru and B are included in the above-described contents. In addition, when Ru and Zr have the above-described contents, the solid solution has a composition ratio in the vicinity of the eutectic point. Therefore, when the protective layer 13 is formed, the solid solution is rapidly cooled, so that the crystalline state becomes amorphous. It is done.

In the above solid solution, when the Ru content and the total content of B and Zr are within the above ranges, the crystalline state of the protective layer 13 becomes amorphous. In the above solid solution, when the total content of B and Zr is less than 5 at%, the content of B and Zr is too low, so that the crystalline state of the protective layer 13 does not become amorphous. On the other hand, when the total content of B and Zr exceeds 30 at%, there arises a problem that the etching resistance of the protective layer 13 is deteriorated. Further, when the Zr content is too large, the etching rate is increased, and when the Zr component is large, there is a problem that oxidation is likely to occur. Moreover, when there is too much content of B, the problem that preparation of the sputtering target used when forming the protective layer 13 will become difficult.
In Patent Document 2, Mo, Nb, etc. other than B and Zr are handled in the same row as B and Zr. However, as a result of our study, it was found that Ti and Nb have a large difference in film formation rate from Ru, and it is practically difficult to increase the amount of Ti and Nb added. In addition, as for Mo, film forming conditions for making it amorphous have not been found yet.
That is, it is estimated that the dopant described in Patent Document 2 is defined in consideration of only one effect, but it is not a dopant that can be practically used. In other words, Patent Document 2 merely exemplifies a dopant that seems to be usable without a technical judgment as to whether or not it can actually be used. Therefore, Patent Document 2 is not described so that a so-called person skilled in the art can understand which dopant can actually be used, and is considered not to be qualified as a known example.

  In the solid solution, the Ru content is 80 at% to 95 at%, the total content of B and Zr is preferably 5 at% to 20 at%, the Ru content is 80 at% to 90 at%, More preferably, the total content of B and Zr is 10 at% to 20 at%.

In this specification, the phrase “the crystalline state of the protective layer 13 is amorphous” includes a microcrystalline structure other than an amorphous structure having no crystal structure.
Note that whether the protective layer 13 is in an amorphous state, that is, an amorphous structure or a microcrystalline structure, can be confirmed by an X-ray diffraction (XRD) method. If the protective layer 13 has an amorphous structure or a microcrystalline structure, a sharp peak is not observed in a diffraction peak obtained by XRD measurement.

  In the EUV mask blank 1 of the present invention, since the protective layer 13 has an amorphous crystal state, formation of a diffusion layer between the outermost layer of the multilayer reflective film constituting the reflective layer 12 and the protective layer 13 is suppressed. When the protective layer 13 has a crystal structure, it is considered that a diffusion layer is formed by diffusion of Si in a general Si layer as the outermost layer of the multilayer reflective film from continuous crystal grain boundaries of the protective layer 13. If the protective layer 13 has an amorphous structure or a microcrystalline structure, there is no crystal grain boundary, or the crystal grain boundary is discontinuous, so that it is difficult for Si to diffuse and the formation of the diffusion layer is suppressed. In particular, the crystalline state is preferably amorphous in the vicinity of the interface with the outermost layer of the multilayer reflective film forming the reflective layer 12.

  If the protective layer 13 has an amorphous structure or a microcrystalline structure in the vicinity of the interface between the outermost layer of the multilayer reflective film forming the reflective layer 12 and the protective layer 13, the effect of suppressing the formation of the diffusion layer is exhibited. it is conceivable that. For this reason, the entire protective layer 13 does not necessarily have an amorphous structure or a microcrystalline structure. For example, only the reflective layer 12 side of the protective layer 13 may have an amorphous structure or a microcrystalline structure, and the absorber layer 14 side (that is, the surface side of the protective layer 13) may have a crystalline structure. Therefore, the protective layer 13 may be a gradient composition film as described below. However, even when the protective layer 13 is a gradient composition film, the entire protective layer 13 preferably has an amorphous structure or a microcrystalline structure. When the entire protective layer 13 has an amorphous structure or a microcrystalline structure, the surface side of the protective layer 13 has an amorphous structure or a microcrystalline structure, so that the surface of the protective layer 13 is excellent in smoothness.

  In this specification, when the protective layer 13 is a gradient composition film, the total content of B and Zr on the reflective layer 12 side is high, and B and Zr on the absorber layer 14 side (that is, the surface side of the protective layer 13). The total content of B and Zr in the solid solution forming the protective layer 13 varies along the thickness direction of the protective layer 13 so that the total content of is reduced. Here, the solid solution forming the protective layer 13 may be any of the solid solutions (A) to (C) described above.

When the protective layer 13 is a gradient composition film, the following effects are exhibited.
Since the reflective layer 12 side of the protective layer 13 has an amorphous structure or a microcrystalline structure, the effect of suppressing the formation of the diffusion layer is exhibited. On the other hand, the oxidation of the surface of the protective layer 13 can be suppressed by lowering the B and Zr content on the surface side of the protective layer 13. If the content of B or Zr is high on the surface side of the protective layer 13, the surface of the protective layer 13 is likely to be oxidized.

In order to exhibit the above effects, the gradient composition film forming the protective layer 13 has the following composition.
(1) On the reflective layer 12 side, the total content of B and Zr in the protective layer 13, that is, in the solid solution is 5 at% to 30 at%.
(2) On the surface side of the protective layer 13 (in FIG. 1, the absorber layer 14 side), the total content of B and Zr in the protective layer 13, that is, in the solid solution, is 0 at% to 20 at%.
Therefore, the surface side of the protective layer 13 may not contain B and Zr.

  In the gradient composition film forming the protective layer 13, the portion having the composition (1) is preferably 1 to 1.5 nm in thickness from the surface on the reflective layer 12 side, and preferably 1 to 2 nm. Further, the Ru content is preferably 80 at% to 95 at%, the total content of B and Zr is preferably 5 at% to 20 at%, the Ru content is 85 at% to 95 at%, and B and Zr It is more preferable that the total content of is 5 at% to 15 at%. On the other hand, the portion having the composition (2) preferably has a thickness of 1 to 1.5 nm, more preferably 1 to 2 nm from the surface on the absorber layer 14 side. Further, the Ru content is preferably 85 at% to 100 at%, the total content of B and Zr is preferably 0 at% to 15 at%, the Ru content is 90 at% to 95 at%, and B and Zr It is more preferable that the total content of is 5 at% to 10 at%.

  The gradient composition film described above may be one in which the total content of B and Zr in the protective layer 13 continuously changes along the thickness direction of the protective layer 13 in the solid solution. A plurality of layers having different total contents of B and Zr in the solid solution may be laminated.

As described above, the diffusion layer may be formed during a heating process (for example, a resist baking process) during mask manufacture or during EUV exposure. Therefore, in these situations, the protective layer 13 needs to maintain an amorphous structure or a microcrystalline structure. When a diffusion layer is formed during EUV exposure, it is necessary to change the exposure conditions in the middle. Therefore, it is particularly important that the protective layer 13 maintain an amorphous structure or a microcrystalline structure during EUV exposure.
When the protective layer 13 contains Ru and B as components, that is, in the case of a solid solution (A), the crystalline state can be maintained up to 200 ° C. in vacuum (1 Pa or less).
In this case, the exposure conditions may be set so that the heating temperature of the protective layer 13 during EUV exposure is 200 ° C. or lower. On the other hand, when the protective layer 13 contains Ru and Zr, that is, in the case of a solid solution (B), the crystalline state can be maintained up to 400 ° C. in vacuum (1 Pa or less). In this case, the exposure conditions may be set so that the heating temperature of the protective layer 13 during EUV exposure is 400 ° C. or lower.
In the case where the protective layer 13 is a gradient composition film, the above is applied to a portion that has been an amorphous structure or a microcrystalline structure from the beginning of the formation of the protective layer 13, that is, the reflective layer side of the protective layer 13.

  In the EUV mask blank 1 of the present invention, the formation of a diffusion layer between the outermost layer of the multilayer reflective film forming the reflective layer 12 and the protective layer 13 during EUV irradiation is suppressed. The decrease is suppressed. Specifically, the reduction in reflectance after irradiating the protective layer 13 with EUV light at an incident angle θ (6 degrees) for 8 hours is preferably 1% or less, and more preferably 0.8% or less. Preferably, it is 0.5% or less.

Since the protective layer 13 has an amorphous structure or a microcrystalline structure, the surface roughness of the surface of the protective layer 13 is 0.5 nm rms or less. If the surface roughness of the surface of the protective layer 13 is large, the surface roughness of the absorber layer 14 formed on the protective layer 13 increases, and the edge roughness of the pattern formed on the absorber layer 14 increases. The dimensional accuracy of the pattern deteriorates. Since the influence of edge roughness becomes more prominent as the pattern becomes finer, the surface of the absorber layer 14 is required to be smooth.
If the surface roughness of the surface of the protective layer 13 is 0.5 nm rms or less, the surface of the absorber layer 14 formed on the protective layer 13 is sufficiently smooth, so that the dimensional accuracy of the pattern deteriorates due to the influence of edge roughness. There is no fear. The surface roughness of the surface of the protective layer 13 is more preferably 0.4 nm rms or less, and further preferably 0.3 nm rms or less.

  The thickness of the protective layer 13 is preferably 1 to 10 nm because the EUV light reflectance is increased and the etching resistance can be obtained. The thickness of the protective layer 13 is more preferably 1 to 5 nm, and further preferably 2 to 4 nm.

In Patent Document 2, since the Ru film can easily form the Si film and the diffusion layer, the addition of Mo or the like to the Ru layer can prevent the formation of the diffusion layer.
However, according to the study by the present inventors, it has been found that the formation of a diffusion layer with the Si layer cannot be prevented only by adding a metal in the Ru film. Details will be described below.
In addition to Mo, Zr and B are specifically exemplified in Patent Document 2 as metals to be added to the Ru layer. Examples thereof are described in Example 5 (RuZr) and Examples 10 to 13 (RuB) of Patent Document 2. However, in Example 5, the Zr content is 50 atomic%, and in Examples 10 to 13, the B content is 30 atomic% (Example 10), 50 atomic% (Example 11), and 60 atoms. % (Example 12) and 66 atomic% (Example 13). That is, in Examples 5 and 10 to 13, the Ru content is very small. In this case, the characteristics inherent to the Ru layer cannot be exhibited.
Further, in Examples 5 and 10 to 13, it is considered that the composition is an intermetallic compound, but according to the study by the present inventors, the intermetallic compound has a specific crystal structure. Therefore, it has been found that the characteristics for preventing Si diffusion are insufficient, and as a result, it is difficult to suppress the decrease in reflectance.
On the other hand, in the present invention, the protective layer is made of Ru and at least one selected from the group consisting of B and Zr as components, and the ratio of each component is set to a specific range, whereby the protective layer is formed. By maintaining the amount of contained Ru to a certain level or more and making the crystal state of the protective layer an amorphous structure, it is possible to prevent the diffusion of Si and consequently suppress the decrease in reflectance.
That is, in the present invention, the protective layer contains ruthenium (Ru) and at least one element selected from the group consisting of boron (B) and zirconium (Zr) as components, and the Ru content in the protective layer Is 70 at% to 95 at%, the total content of B and Zr is 5 at% to 30 at%, and the crystal structure of the protective layer is amorphous.
In the present invention, the protective layer contains Ru and at least one element selected from the group consisting of B and Zr as components, and the total content of B and Zr on the reflective layer side is high, and on the surface side A gradient composition film in which the total content of B and Zr in the protective layer varies along the thickness direction of the protective layer so that the total content of B and Zr is low; The total content of Zr is 5 at% to 30 at%, the total content of B and Zr on the surface side is 0 at% to 20 at%, and the crystal structure of the protective layer is amorphous.

The protective layer 13 can be formed using a known film formation method such as a magnetron sputtering method or an ion beam sputtering method.
When the protective layer 13 made of the above-described solid solution (A) is formed by magnetron sputtering, a Ru target and a B target may be used as targets and these targets may be simultaneously discharged in an argon (Ar) atmosphere. Specifically, magnetron sputtering may be performed under the following conditions.
Sputtering gas: Ar (gas pressure 1.0 × 10 ⁻¹ to 10 × 10 ⁻¹ Pa, preferably 1.0 × 10 ^{−1 to} 5.0 × 10 ⁻¹ Pa, more preferably 1.0 × 10 ^{− 1 to} 3.0 × 10 ⁻¹ Pa)
Input power (for each target): 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 1.0-60 nm / sec, preferably 1.0-45 nm / sec, more preferably 1.0-30 nm / sec

When the protective layer 13 made of the above-described solid solution (B) is formed by magnetron sputtering, a Ru target and a Zr target may be used as targets, and these targets may be discharged simultaneously in an Ar atmosphere. Specifically, magnetron sputtering may be performed under the following conditions.
Sputtering gas: Ar (gas pressure 1.0 × 10 ⁻¹ to 10 × 10 ⁻¹ Pa, preferably 1.0 × 10 ^{−1 to} 5.0 × 10 ⁻¹ Pa, more preferably 1.0 × 10 ^{− 1 to} 3.0 × 10 ⁻¹ Pa)
Input power (for each target): 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 1.0-60 nm / sec, preferably 1.0-45 nm / sec, more preferably 1.0-30 nm / sec

The characteristic particularly required for the absorber layer 14 is that the EUV light reflectance is extremely low. Specifically, when the surface of the absorber layer 14 is irradiated with light in the wavelength region of EUV light, the maximum light reflectance near a wavelength of 13.5 nm is preferably 0.5% or less, 0.1% The following is more preferable.
In order to achieve the above-mentioned characteristics, it is preferable that the material is composed of a material having a high EUV light absorption coefficient, and it is preferable that the material is mainly composed of tantalum (Ta).
Examples of the absorber layer 14 include those containing Ta, B, Si, and nitrogen (N) in the ratios described below (TaBSiN film).
B content 1 at% or more and less than 5 at%, preferably 1 to 4.5 at%, more preferably 1.5 to 4 at%
Si content 1-25 at%, preferably 1-20 at%, more preferably 2-12 at%
Composition ratio of Ta and N (Ta: N) 8: 1 to 1: 1
Ta content preferably 50 to 90 at%, more preferably 60 to 80 at%
N content preferably 5-30 at%, more preferably 10-25 at%

The absorber layer 14 having the above composition has an amorphous crystal state and excellent surface smoothness.
The absorber layer 14 having the above composition has a surface roughness of 0.5 nm rms or less. If the surface roughness of the surface of the absorber layer 14 is large, the edge roughness of the pattern formed on the absorber layer 14 increases, and the dimensional accuracy of the pattern deteriorates. Since the influence of edge roughness becomes more prominent as the pattern becomes finer, the surface of the absorber layer 14 is required to be smooth.
If the surface roughness of the surface of the absorber layer 14 is 0.5 nm rms or less, the surface of the absorber layer 14 is sufficiently smooth, and there is no possibility that the dimensional accuracy of the pattern is deteriorated due to the influence of edge roughness. The surface roughness of the absorber layer 14 surface is more preferably 0.4 nm rms or less, and further preferably 0.3 nm rms or less.

The thickness of the absorber layer 14 is preferably 50 to 100 nm. The absorption layer 14 having the above-described configuration can be formed using a known film formation method such as a sputtering method such as a magnetron sputtering method or an ion beam sputtering method. When the magnetron sputtering method is used, the absorber layer 14 can be formed by the following methods (1) to (3).
(1) The absorber layer 14 is formed by simultaneously discharging these individual targets in a nitrogen (N ₂ ) atmosphere diluted with Ar using a Ta target, a B target, and a Si target.
(2) Using the TaB compound target and the Si target, the absorber layer 14 is formed by simultaneously discharging these targets in an N ₂ atmosphere diluted with Ar.
(3) Using the TaBSi compound target, the absorber layer 14 is formed by discharging the target in which these three elements are integrated in an N ₂ atmosphere diluted with Ar.
Of the methods described above, in the method of simultaneously discharging two or more targets ((1), (2)), the composition of the absorber layer 14 to be formed is controlled by adjusting the input power of each target. can do.
Among these, the methods (2) and (3) are preferable from the viewpoint of avoiding unstable discharge and variations in film composition and film thickness, and the method (3) is particularly preferable. The composition of the TaBSi compound target is Ta = 50 to 94 at%, Si = 5 to 30 at%, and B = 1 to 20 at%, thereby avoiding unstable discharge and variations in film composition and film thickness. Particularly preferred in terms.

In order to form the absorber layer 14 by the above exemplified method, specifically, the following film forming conditions may be used.
Method using TaB compound target and Si target (2)
Sputtering gas: Ar and N ₂ mixed gas (N ₂ gas concentration: 3 to 80 vol%, preferably 5 to 30 vol%, more preferably 8 to 15 vol%. Gas pressure: 1.0 × 10 ⁻¹ Pa to 10 × 10 ^{− 1} Pa, preferably ^{1.0 × 10 -1 Pa~5 × 10 -1} Pa, more preferably ^{1.0 × 10 -1 Pa~3 × 10 -1} Pa.)
Input power (for each target): 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-60 nm / sec, preferably 3.5-45 nm / sec, more preferably 5-30 nm / sec
Method using TaBSi compound target (3)
Sputtering gas: Ar and N ₂ mixed gas (N ₂ gas concentration: 3 to 80 vol%, preferably 5 to 30 vol%, more preferably 8 to 15 vol%. Gas pressure: 1.0 × 10 ⁻¹ Pa to 10 × 10 ^{− 1} Pa, preferably ^{1.0 × 10 -1 Pa~5 × 10 -1} Pa, more preferably ^{1.0 × 10 -1 Pa~3 × 10 -1} Pa)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-60 nm / sec, preferably 3.5-45 nm / sec, more preferably 5-30 nm / sec

As for the EUV mask blank of this invention, as shown in FIG. 2, it is preferable that the low reflection layer 15 in the test | inspection light used for the test | inspection of a mask pattern is formed on the absorber layer 14. As shown in FIG.
When producing an EUV mask, after forming a pattern in an absorber layer, it is inspected whether this pattern is formed as designed. In this mask pattern inspection, an inspection machine that normally uses light of about 257 nm as inspection light is used. That is, the difference in reflectance of light of about 257 nm, specifically, the surface where the absorber layer 14 is removed by pattern formation and the surface of the absorber layer 14 that remains without being removed by pattern formation, It is inspected by the difference in reflectance. Here, the former is the surface of the protective layer 13. Therefore, if the difference in reflectance between the surface of the protective layer 13 and the surface of the absorber layer 14 with respect to the wavelength of the inspection light is small, the contrast at the time of inspection deteriorates and accurate inspection cannot be performed.

The absorber layer 14 having the above-described configuration has extremely low EUV light reflectance, and has excellent characteristics as an absorption layer of the EUV mask blank 1. However, when viewed with respect to the wavelength of inspection light, the light reflectance is not necessarily high. It's not low enough. As a result, the difference between the reflectance of the surface of the absorber layer 14 and the reflectance of the surface of the protective layer 13 at the wavelength of the inspection light becomes small, and there is a possibility that sufficient contrast during the inspection cannot be obtained. If sufficient contrast at the time of inspection is not obtained, pattern defects cannot be sufficiently determined in mask inspection, and accurate defect inspection cannot be performed.
By forming the low reflection layer 15 on the absorber layer 14, the contrast at the time of inspection becomes good. In other words, the light reflectance at the wavelength of the inspection light becomes extremely low. The low reflection layer 15 formed for such a purpose has a maximum light reflectance of 15% or less, preferably 10% or less when irradiated with light in the wavelength region of inspection light. More preferably, it is 5% or less.
If the light reflectance at the wavelength of the inspection light in the low reflection layer 15 is 15% or less, the contrast at the time of the inspection is good. Specifically, the contrast between the reflected light having the wavelength of the inspection light on the surface of the protective layer 13 and the reflected light having the wavelength of the inspection light on the surface of the low reflective layer 15 is 40% or more.

In this specification, the contrast can be obtained using the following equation.
Contrast (%) = ((R ₂ −R ₁ ) / (R ₂ + R ₁ )) × 100
Here, R _{2 at} the wavelength of the inspection light is the reflectance at the surface of the protective layer 13, and R ₁ is the reflectance at the surface of the low reflective layer 15. Note that R ₁ and R ₂ are measured in a state where patterns are formed on the absorber layer 14 and the low reflection layer 15 of the EUV mask blank 1 shown in FIG. 2 (that is, the state shown in FIG. 3). The R ₂ is a value measured on the surface of the protective layer 13 exposed to the outside after the absorber layer 14 and the low reflection layer 15 are removed by pattern formation in FIG. 3, and R ₁ is not removed by pattern formation. It is a value measured on the surface of the remaining low reflection layer 15.
In the present invention, the contrast represented by the above formula is more preferably 45% or more, further preferably 60% or more, and particularly preferably 80% or more.

In order to achieve the above characteristics, the low reflection layer 15 is preferably made of a material whose refractive index at the wavelength of the inspection light is lower than that of the absorber layer 14, and its crystal state is preferably amorphous.
Specific examples of such a low reflection layer 15 include those containing Ta, B, Si and oxygen (O) in the ratios described below (low reflection layer (TaBSiO)).
B content 1 at% or more and less than 5 at%, preferably 1 to 4.5 at%, more preferably 1.5 to 4 at%
Si content 1-25 at%, preferably 1-20 at%, more preferably 2-10 at%
Composition ratio of Ta and O (Ta: O) 7: 2 to 1: 2, preferably 7: 2 to 1: 1, more preferably 2: 1 to 1: 1

Specific examples of the low reflective layer 15 include those containing Ta, B, Si, O, and N in the ratios described below (low reflective layer (TaBSiON)).
Content of B 1 at% or more and less than 5 at%, preferably 1 to 4.5 at%, more preferably 2 to 4.0 at%
Si content 1-25 at%, preferably 1-20 at%, more preferably 2-10 at%
Composition ratio of Ta, O and N (Ta: (O + N)) 7: 2 to 1: 2, preferably 7: 2 to 1: 1, more preferably 2: 1 to 1: 1

Since the low reflection layers (TaBSiO) and (TaBSiON) have the above-described configuration, the crystal state thereof is amorphous and the surface thereof is excellent in smoothness. Specifically, the surface roughness of the low reflective layer (TaBSiO), (TaBSiON) surface is 0.5 nm rms or less.
As described above, the surface of the absorber layer 14 is required to be smooth in order to prevent deterioration in the dimensional accuracy of the pattern due to the influence of edge roughness. Since the low reflection layer 15 is formed on the absorber layer 14, the surface thereof is required to be smooth for the same reason.
If the surface roughness of the surface of the low reflection layer 15 is 0.5 nm rms or less, the surface of the low reflection layer 15 is sufficiently smooth, so that the dimensional accuracy of the pattern does not deteriorate due to the influence of edge roughness. The surface roughness of the surface of the low reflective layer 15 is more preferably 0.4 nm rms or less, and further preferably 0.3 nm rms or less.

  When the low reflection layer 15 is formed on the absorber layer 14, the total thickness of the absorber layer 14 and the low reflection layer 15 is preferably 55 to 130 nm. Further, if the thickness of the low reflection layer 15 is larger than the thickness of the absorber layer 14, the EUV light absorption characteristics in the absorber layer 14 may be deteriorated. Therefore, the thickness of the low reflection layer 15 is determined by the absorber layer. It is preferred that the thickness be less than 14. For this reason, it is preferable that the thickness of the low reflection layer 15 is 5-30 nm, and it is more preferable that it is 10-20 nm.

The low reflective layers (TaBSiO) and (TaBSiON) can be formed using a known film forming method such as a sputtering method such as a magnetron sputtering method or an ion beam sputtering method. The low reflection layer (TaBSiO) can be formed by the methods 1) to (3).
(1) Using a Ta target, B target and Si target, a low reflective layer (TaBSiO) is formed by simultaneously discharging these individual targets in an oxygen (O ₂ ) atmosphere diluted with argon (Ar). .
(2) A TaB compound target and a Si target are used, and these targets are simultaneously discharged in an oxygen atmosphere diluted with argon to form a low reflective layer (TaBSiO).
(3) Using a TaBSi compound target, the target integrated with these three elements is discharged in an oxygen atmosphere diluted with argon to form a low reflective layer (TaBSiO).
Of the methods described above, in the method of simultaneously discharging two or more targets ((1), (2)), the composition of the low reflection layer (TaBSiO) formed by adjusting the input power of each target. Can be controlled.
Among these, the methods (2) and (3) are preferable from the viewpoint of avoiding unstable discharge and variations in film composition and film thickness, and the method (3) is particularly preferable. The composition of the TaBSi compound target is Ta = 50 to 94 at%, Si = 5 to 30 at%, and B = 1 to 20 at%, thereby avoiding unstable discharge and variations in film composition and film thickness. Particularly preferred in terms.
When forming the low reflection layer (TaBSiON), the same procedure as described above may be performed in an oxygen / nitrogen mixed gas atmosphere diluted with argon instead of an oxygen atmosphere diluted with argon.

In order to form the low reflection layer (TaBSiO) by the above method, specifically, the following film formation conditions may be used.
Method using TaB compound target and Si target (2)
Sputtering gas: Ar and O ₂ mixed gas (O ₂ gas concentration 3 to 80 vol%, preferably 5 to 30 vol%, more preferably 8 to 15 vol%. Gas pressure 1.0 × 10 ⁻¹ Pa to 10 × 10 ^{− 1} Pa, preferably ^{1.0 × 10 -1 Pa~5 × 10 -1} Pa, more preferably ^{1.0 × 10 -1 Pa~3 × 10 -1} Pa.)
Input power (for each target): 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-60 nm / sec, preferably 3.5-45 nm / sec, more preferably 5-30 nm / sec
Method using TaBSi compound target (3)
Sputtering gas: Ar and O ₂ mixed gas (O ₂ gas concentration 3 to 80 vol%, preferably 5 to 30 vol%, more preferably 8 to 15 vol%. Gas pressure 1.0 × 10 ⁻¹ Pa to 10 × 10 ^{− 1} Pa, preferably ^{1.0 × 10 -1 Pa~5 × 10 -1} Pa, more preferably ^{1.0 × 10 -1 Pa~3 × 10 -1} Pa.)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-50 nm / sec, preferably 2.5-35 nm / sec, more preferably 5-25 nm / sec

In order to form the low reflection layer (TaBSiON) by the above method, specifically, the following film formation conditions may be used.
Method using TaB compound target and Si target (2)
Sputtering gas: Ar, O ₂ and N ₂ mixed gas (O ₂ gas concentration 5 to 30% by volume, N ₂ gas concentration 5 to 30% by volume, preferably O ₂ gas concentration 6 to 25% by volume, N ₂ gas concentration 6-25 vol%, more preferably O ₂ gas concentration 10-20 vol%, N ₂ gas concentration 15 to 25 vol%. gas pressure ^{1.0 × 10 -2 Pa~10 × 10 -2} Pa, preferably 1 ^{.0 × 10 -2 Pa~5 × 10 -2} Pa, and more preferably ^{1.0 × 10 -2 Pa~3 × 10 -2} Pa.)
Input power (for each target): 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-50 nm / sec, preferably 2.5-35 nm / sec, more preferably 5-25 nm / sec
Method using TaBSi compound target (3)
Sputtering gas: Ar, O ₂ and N ₂ mixed gas (O ₂ gas concentration 5 to 30% by volume, N ₂ gas concentration 5 to 30% by volume, preferably O ₂ gas concentration 6 to 25% by volume, N ₂ gas concentration 6-25 vol%, more preferably O ₂ gas concentration 10-20 vol%, N ₂ gas concentration 15 to 25 vol%. gas pressure ^{1.0 × 10 -2 Pa~10 × 10 -2} Pa, preferably 1 ^{.0 × 10 -2 Pa~5 × 10 -2} Pa, and more preferably ^{1.0 × 10 -2 Pa~3 × 10 -2} Pa.)
Input power: 30 to 1000 W, preferably 50 to 750 W, more preferably 80 to 500 W
Deposition rate: 2.0-50 nm / sec, preferably 2.5-35 nm / sec, more preferably 5-25 nm / sec

  In the EUV mask blank 1 shown in FIG. 2, the low reflection layer 15 is preferably formed on the absorber layer 14 because the wavelength of the inspection light for the pattern and the wavelength of the EUV light are different. Therefore, when EUV light (around 13.5 nm) is used as the pattern inspection light, it is considered unnecessary to form the low reflection layer 15 on the absorber layer 14. The wavelength of the inspection light tends to shift to the short wavelength side as the pattern size becomes smaller, and it is conceivable that it will shift to 193 nm and further to 13.5 nm in the future. When the wavelength of the inspection light is 13.5 nm, it is considered unnecessary to form the low reflection layer 15 on the absorber layer 14.

The EUV mask blank 1 of the present invention may have a functional film known in the field of EUV mask blanks in addition to the reflective layer 12, the protective layer 13, and the absorber layer 14. As a specific example of such a functional film, for example, as described in JP-A-2003-501823, a high dielectric applied to the back side of the substrate in order to promote electrostatic chucking of the substrate. A functional coating. Here, the back surface of the substrate refers to the surface of the substrate 11 in FIG. 1 opposite to the side on which the reflective layer 12 is formed. For the high dielectric coating applied to the back surface of the substrate for such a purpose, the electrical conductivity and thickness of the constituent material are selected so that the sheet resistance is 100Ω / □ or less. The constituent material of the high dielectric coating can be widely selected from those described in known literature. For example, a high dielectric constant coating described in JP-A-2003-501823, specifically, a coating made of silicon, TiN, molybdenum, chromium, or TaSi can be applied. The thickness of the high dielectric coating can be, for example, 10 to 1000 nm.
The high dielectric coating can be formed using a known film forming method, for example, a sputtering method such as a magnetron sputtering method or an ion beam sputtering method, a CVD method, a vacuum evaporation method, or an electrolytic plating method.

  In addition to the EUV mask blank described above, the present invention also provides a substrate with a reflective film used for manufacturing the EUV mask blank, and an EUV mask patterned on the EUV mask blank. Here, the substrate with a reflective film refers to the state before the absorber layer is formed in the above EUV mask blank, that is, the substrate excluding the absorber layer 14 in FIG.

The present invention will be further described below using examples.
Example 1
In this example, the EUV mask blank 1 shown in FIG. 2 was produced.
As the substrate 11 for film formation, a SiO ₂ —TiO ₂ glass substrate (outer dimensions 6 inches (152.4 mm) square, thickness 6.3 mm) was used. This glass substrate has a thermal expansion coefficient of 0.2 × 10 ⁻⁷ / ° C., a Young's modulus of 67 GPa, a Poisson's ratio of 0.17, and a specific rigidity of 3.07 × 10 ⁷ m ² / s ² . This glass substrate was polished to form a smooth surface with an rms of 0.15 nm or less and a flatness of 100 nm or less.

A high dielectric coating (not shown) having a sheet resistance of 100Ω / □ was applied to the back surface of the substrate 11 by depositing a Cr film having a thickness of 100 nm using a magnetron sputtering method.
A substrate 11 (outer dimensions 6 inches (152.4 mm) square, thickness 6.3 mm) is fixed to a normal electrostatic chuck having a flat plate shape by using the formed Cr film, and ions are formed on the surface of the substrate 11. Si / Mo multilayer reflective film (reflective layer) having a total film thickness of 272 nm ((4.5 nm + 2.3 nm) × 40) is obtained by repeating 40 cycles of alternately forming Si films and Mo films using beam sputtering. 12) was formed. The uppermost layer was a Si film to prevent Mo oxidation.

The conditions for forming the Si film and the Mo film are as follows.
Conditions for forming the Si film Target: Si target (boron doped)
Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 700V
Deposition rate: 0.077 nm / sec
Film thickness: 4.5nm
Conditions for forming the Mo film Target: Mo target Sputtering gas: Ar gas (gas pressure 0.02 Pa)
Voltage: 700V
Deposition rate: 0.064 nm / sec
Film thickness: 2.3 nm

Next, the protective layer 13 made of the solid solution (A) was formed on the reflective layer 12 by using a magnetron sputtering method.
The formation conditions of the protective layer 13 are as follows.
Target: Ru target, B target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output: 30W (Ru target), RF250W (B target)
Deposition rate: 4.8 nm / sec
Film thickness: 2.5nm

The following evaluation was implemented with respect to the protective layer 13 obtained by said procedure.
(1) Film composition The composition of the protective layer 13 was measured using an X-ray photoelectron spectrometer (manufactured by PERKIN ELMER-PHI: No. 5500). The composition ratio (at%) of the protective layer 13 was Ru: B = 87.5: 12.5.
(2) Crystal structure The crystal structure of the protective layer 13 was confirmed with an X-ray diffractometer (manufactured by RIGAKU). The crystal structure was confirmed by using a film made of a solid solution (A) having a thickness of 100 nm on a silicon substrate under the above film forming conditions. Since no sharp peak was observed in the obtained diffraction peak, it was confirmed that the crystal structure of the protective layer 13 was an amorphous structure or a microcrystalline structure. Furthermore, when a heating test was performed under vacuum conditions (1 Pa or less), the amorphous structure or microcrystalline structure was maintained up to 200 ° C.
(3) Surface roughness The surface roughness of the protective layer 13 was confirmed using an atomic force microscope (manufactured by Seiko Instruments Inc .: No. SPI3800) in accordance with JIS-B0601 (1994). The surface roughness of the protective layer 13 was 0.15 nm rms.
(4) EUV resistance EUV light (synchrotron radiation) was irradiated to the surface of the protective layer 13 at an incident angle θ (6 degrees) for 8 hours. After EUV light irradiation, the decrease in EUV reflectance was 0.5% or less.

Next, a TaBSiN layer was formed as the absorber layer 14 on the protective layer 13 by using a magnetron sputtering method.
The conditions for forming the TaBSiN layer are as follows.
Film formation conditions for TaBSiN layer Target: TaBSi compound target (composition ratio: Ta 80 at%, B 10 at%, Si 10 at%)
Sputtering gas: Ar and N ₂ mixed gas (Ar: 86% by volume, N ₂ : 14% by volume, gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 7.4 nm / sec
Film thickness: 60nm

The following evaluation was implemented with respect to the absorber layer 14 (TaBSiN layer) obtained by said procedure.
(1) Film composition The composition of the absorber layer 14 (TaSiBN layer) was measured using an X-ray photoelectron spectrometer (manufactured by PERKIN ELEMER-PHI: number 5500). The composition ratio (at%) of the absorber layer 14 is Ta: B: Si: N = 70: 3: 10: 17.

(2) Crystal structure The crystal structure of the absorber layer 14 (TaSiBN film) was confirmed with an X-ray diffractometer (X-Ray Diffractometer) (manufactured by RIGAKU). Since no sharp peak was observed in the obtained diffraction peak, it was confirmed that the crystal structure of the absorber layer 14 was an amorphous structure or a microcrystalline structure.

(3) Surface roughness The surface roughness of the absorber layer 14 (TaSiBN film) is measured using an atomic force microscope (manufactured by Seiko Instruments Inc .: No. SPI3800) in accordance with JIS-B0601 (1994). Confirmed. The surface roughness of the absorber layer 14 was 0.15 nm rms.

Finally, by forming a TaBSiON layer as the low reflective layer 15 on the absorber 14, the EUV in which the reflective layer 12, the protective layer 13, the absorber layer 14, and the low reflective layer 15 are formed in this order on the substrate 11. Mask blank 1 was obtained.
The film forming conditions for the TaBSiON layer are as follows.
Film formation conditions for TaBSiON layer Target: TaBSi target (composition ratio: Ta 80 at%, B 10 at%, Si 10 at%)
Sputtering gas: Mixed gas of Ar, N ₂ and O ₂ (Ar: 60% by volume, N ₂ : 20% by volume, O ₂ : 20% by volume, gas pressure: 0.3 Pa)
Input power: 150W
Deposition rate: 11 nm / sec
Film thickness: 10nm

  When the composition ratio (at%) of the low reflection layer 15 obtained by the above procedure was measured using an X-ray photoelectron spectrometer (manufactured by PERKIN ELEMER-PHI: number 5500), Ta: B: Si: N: O = 40: 3: 10: 10: 37.

Reflection characteristics (contrast evaluation)
When the protective layer 13 was formed, the reflectance of the pattern inspection light (wavelength 257 nm) on the surface of the protective layer 13 was measured using a spectrophotometer. Moreover, after forming the low reflection layer 15 (TaBSiON layer), the reflectance of the pattern inspection light on the surface of the low reflection layer 15 was measured. As a result, the reflectance on the surface of the protective layer 13 was 60.0%, and the reflectance on the surface of the low reflective layer 15 was 6.9%. Using these results and the above formula, the contrast was determined to be 79.4%.

Etching characteristics The etching characteristics were evaluated by the following method instead of using the EUV mask blank produced by the above procedure.
On a sample stage (4 inch quartz substrate) of an RF plasma etching apparatus, a Si chip (10 mm × 30 mm) on which a film made of a solid solution (A) is formed as a sample and (2) a TaBSiN film are formed. A Si chip (10 mm × 30 mm) was installed. In this state, the film made of the solid solution (A) and the TaNBSiN film on the Si chip placed on the sample stage were subjected to plasma etching (RF plasma etching) under the following conditions.
Bias RF: 50W
Etching time: 120 sec
Trigger pressure: 3Pa
Etching pressure: 1Pa
Etching gas: Cl ₂ / Ar
Gas flow rate (Cl ₂ / Ar): 20/80 sccm
Distance between electrode substrates: 55 mm

The film made of the solid solution (A) and the TaBSiN film were formed by magnetron sputtering as described above. The etching rate was calculated | required about the film | membrane consisting of the formed solid solution (A), and the TaBSiN film | membrane, and the etching selectivity was calculated | required using the following formula.
Etching selectivity = (etching rate of TaBSiN film) / (etching rate of film made of solid solution (A))
In the case of plasma etching, the etching selectivity between the absorber layer 14 and the protective layer 13 is desirably 10 or more. The etching selectivity of the film made of the TaBSiN film and the solid solution (A) was 15, and had a sufficient etching selectivity.

Example 2
Example 2 was performed in the same procedure as Example 1 except that the protective layer 13 made of the solid solution (B) was used. The protective layer 13 made of the solid solution (B) was formed by the magnetron sputtering method under the following conditions.
Conditions for forming protective layer 13 Target: Ru target, Zr target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output: 150W (Ru target), 100W (Zr target)
Deposition rate: 18.2 nm / sec
Film thickness: 2.5nm

The following evaluation was implemented with respect to the protective layer 13 obtained by said procedure.
(1) Film composition The composition of the protective layer 13 was measured using an X-ray photoelectron spectrometer (manufactured by PERKIN ELMER-PHI: No. 5500). The composition ratio (at%) of the protective layer 13 is Ru: Zr = 80.4: 19.6.
(2) Crystal structure The crystal structure of the protective layer 13 was confirmed with an X-ray diffractometer (manufactured by RIGAKU). The crystal structure was confirmed by using a film made of a solid solution (B) having a thickness of 100 nm on a silicon substrate under the above film forming conditions. Since no sharp peak was observed in the obtained diffraction peak, it was confirmed that the crystal structure of the protective layer 13 was an amorphous structure or a microcrystalline structure. Furthermore, when a heating test was performed at 1 Pa or less, the amorphous structure or the microcrystalline structure was maintained up to 400 ° C.
(3) Surface roughness The surface roughness of the protective layer 13 was confirmed using an atomic force microscope (manufactured by Seiko Instruments Inc .: No. SPI3800) in accordance with JIS-B0601 (1994). The surface roughness of the protective layer 13 was 0.15 nm rms.
(4) EUV resistant EUV light (synchrotron radiation) was irradiated on the surface of the protective layer 13 at an incident angle θ (6 degrees) for the same time as in Example 1. After EUV light irradiation, the decrease in EUV reflectance was 0.5% or less.
(5) Reflection characteristics Further, the reflectance of the pattern inspection light (wavelength 257 nm) on the surfaces of the protective layer 13 and the low reflection layer 15 (TaBSiON layer) was measured in the same procedure as in Example 1. As a result, the reflectance on the surface of the protective layer 13 was 60.0%, and the reflectance on the surface of the low reflective layer 15 was 6.9%. Using these results and the above formula, the contrast was determined to be 79.4%.
(6) Etching characteristics The etching characteristics of the film made of the solid solution (B) were evaluated in the same procedure as described above. As a result, the etching selectivity between the TaBSiN film and the film made of the solid solution (B) was 11.5, which was a sufficient etching selectivity.

Comparative Example 1
Comparative Example 1 was carried out in the same procedure as Example 1 except that a film made of a solid solution (A) having a B content of less than 5 at% was used as the protective layer 13. The protective layer 13 was formed under the following conditions.
Conditions for forming protective layer 13 Target: Ru target, B target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output: 30W (Ru target), RF150W (B target)
Deposition rate: 4.8 nm / sec
Film thickness: 2.5nm

The composition of the obtained protective layer 13 was measured using an X-ray Photoelectron Spectrometer (manufactured by PERKIN ELEMER-PHI: number 5500). The composition ratio (at%) of the protective layer 13 was Ru: B = 95.2: 4.8.
When the crystal structure of the obtained protective layer 13 was confirmed with an X-ray diffractometer, a sharp peak was observed in the obtained diffraction peak, indicating that the protective layer 13 was crystalline. It could be confirmed. The crystal structure was confirmed by using a film made of a solid solution (A) formed on a silicon substrate with a thickness of 100 nm under the above conditions.
The obtained protective layer 13 was examined for EUV resistance in the same procedure as in Example 1. As a result, the reflectance was reduced by 2% due to irradiation for the same time as in Example 1, and it was confirmed that the EUV resistance was inferior. It was done.

Comparative Example 2
Comparative Example 2 was carried out in the same procedure as in Example 1 except that a film made of a solid solution (A) having a B content of more than 30 at% was used as the protective layer 13, but the protective layer 13 could be formed. There wasn't.
Conditions for forming protective layer 13 Target: Ru target, B target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output: 30W (Ru target), RF400W (B target)
Deposition rate: 5.0 nm / sec
Film thickness: 2.5nm

Comparative Example 3
Comparative Example 3 was performed in the same procedure as Example 2 except that a film made of a solid solution (B) having a Zr content of less than 5 at% was used as the protective layer 13. The protective layer 13 was formed under the following conditions.
Conditions for forming protective layer 13 Target: Ru target, Zr target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output: 150W (Ru target), 50W (Zr target)
Deposition rate: 15.8 nm / sec
Film thickness: 2.5nm

The composition of the obtained protective layer 13 was measured using an X-ray Photoelectron Spectrometer (manufactured by PERKIN ELEMER-PHI: number 5500). The composition ratio (at%) of the protective layer 13 was Ru: Zr = 96: 4.
When the crystal structure of the obtained protective layer 13 was confirmed with an X-ray diffractometer, a sharp peak was observed in the obtained diffraction peak, indicating that the protective layer 13 was crystalline. It could be confirmed. For confirmation of the crystal structure, a film made of a solid solution (B) having a Zr content of less than 5 at% under the above conditions was formed on a silicon substrate to a thickness of 100 nm.
The obtained protective layer 13 was examined for EUV resistance in the same procedure as in Example 2. As a result, the reflectance decreased by 2% by irradiation for the same time as in Example 1, and it was confirmed that the EUV resistance was inferior. It was done.

Comparative Example 4
Comparative Example 4 was carried out in the same procedure as Example 2 except that a film made of a solid solution (B) having a Zr content of more than 30 at% was used as the protective layer 13. The protective layer 13 was formed under the following conditions.
Conditions for forming protective layer 13 Target: Ru target, Zr target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output: 24W (Ru target), 150W (Zr target)
Deposition rate: 10.9nm / sec
Film thickness: 2.5nm

The composition of the obtained protective layer 13 was measured using an X-ray Photoelectron Spectrometer (manufactured by PERKIN ELEMER-PHI: number 5500). The composition ratio (at%) of the protective layer 13 was Ru: Zr = 58: 42.
The etching characteristics of the film made of the solid solution (B) having a Zr content exceeding 30 at% were evaluated in the same procedure as described above. As a result, the etching selectivity between the TaBSiN film and the film made of the solid solution (B) was 5.6, and a sufficient etching selectivity was not obtained.

Comparative Example 5
Comparative Example 5 was carried out in the same procedure as Example 2 except that a film containing Ru and Ti was used as the protective layer 13. In order to adjust the Ti content of the protective layer 13, the target output was performed under the following three conditions.
Conditions for forming protective layer 13 Target: Ru target, Ti target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output condition (1): 150 W (Ru target), 50 W (Ti target)
Output condition (2): 150 W (Ru target), 100 W (Ti target)
Output condition (3): 50 W (Ru target), 150 W (Ti target)
Film thickness: 2.5nm

  When the crystal structure of the obtained protective layer 13 was confirmed with an X-ray diffractometer, a sharp peak was observed in the obtained diffraction peak, indicating that the protective layer 13 was crystalline. It could be confirmed. The crystal structure was confirmed by using a 100 nm thick film containing Ru and Ti formed on a silicon substrate under the above film forming conditions.

Comparative Example 6
Comparative Example 5 was carried out in the same procedure as Example 2 except that a film containing Ru and Mo was used as the protective layer 13. In addition, in order to adjust the content rate of Mo of the protective layer 13, the target output was implemented on the following three conditions.
Conditions for forming protective layer 13 Target: Ru target, Mo target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output condition (1): 150 W (Ru target), 50 W (Mo target)
Output condition (2): 150 W (Ru target), 100 W (Mo target)
Output condition (3): 150 W (Ru target), 150 W (Mo target)
Film thickness: 2.5nm

  When the crystal structure of the obtained protective layer 13 was confirmed with an X-ray diffractometer, a sharp peak was observed in the obtained diffraction peak, indicating that the protective layer 13 was crystalline. It could be confirmed. The crystal structure was confirmed by using a film having a thickness of 100 nm containing Ru and Mo formed on a silicon substrate under the above film forming conditions.

Comparative Example 7
Comparative Example 5 was carried out in the same procedure as Example 2 except that a film containing Ru and Nb was used as the protective layer 13. In addition, in order to adjust the content rate of Nb of the protective layer 13, target output was implemented on the following three conditions.
Conditions for forming protective layer 13 Target: Ru target, Nb target Sputtering gas: Ar gas (gas pressure: 2 mTorr (2.6 × 10 ⁻¹ Pa))
Output condition (1): 150 W (Ru target), 30 W (Nb target)
Output condition (2): 150 W (Ru target), 50 W (Nb target)
Output condition (3): 150 W (Ru target), 100 W (Nb target)
Film thickness: 2.5nm

  When the crystal structure of the obtained protective layer 13 was confirmed with an X-ray diffractometer, a sharp peak was observed in the obtained diffraction peak, indicating that the protective layer 13 was crystalline. It could be confirmed. The crystal structure was confirmed by using a 100 nm thick film containing Ru and Nb formed on a silicon substrate under the above film forming conditions.

FIG. 1 is a schematic cross-sectional view showing an embodiment of an EUV mask blank of the present invention. FIG. 2 is a view similar to FIG. However, a low reflection layer is formed on the absorber layer. FIG. 3 shows a state where a pattern is formed on the absorber layer 14 (and the low reflection layer 15) of the EUV mask blank 1 of FIG.

Explanation of symbols

1: EUV mask blank 11: Substrate 12: Reflective layer (multilayer reflective film)
13: Protective layer 14: Absorber layer 15: Low reflective layer

Claims (17)

A substrate with a reflective layer for EUV lithography in which a reflective layer that reflects EUV light and a protective layer that protects the reflective layer are formed in this order on the substrate,
The protective layer contains ruthenium (Ru) and at least one element selected from the group consisting of boron (B) and zirconium (Zr) as components,
A substrate with a reflective layer for EUV lithography, wherein the protective layer has a Ru content of 70 at% to 95 at% and a total content of B and Zr of 5 at% to 30 at%. A substrate with a reflective layer for EUV lithography in which a reflective layer that reflects EUV light and a protective layer that protects the reflective layer are formed in this order on the substrate,
The protective layer contains Ru and at least one element selected from the group consisting of B and Zr,
The total content of B and Zr in the protective layer is such that the total content of B and Zr on the reflective layer side is high and the total content of B and Zr on the surface side is low. A gradient composition film that varies along the thickness direction of the layer,
The total content of B and Zr on the reflective layer side is 5 at% to 30 at%,
A substrate with a reflective layer for EUV lithography, wherein the total content of B and Zr on the surface side is 0 at% to 20 at%. The substrate with a reflective layer for EUV lithography according to claim 1, wherein the protective layer is made of any of the following solid solutions.
Solid solution of Ru and B Solid solution of Ru and Zr Solid solution of Ru, B and Zr   The substrate with a reflective layer for EUV lithography according to any one of claims 1 to 3, wherein the crystal state of the protective layer is amorphous. A substrate with a reflective layer for EUV lithography in which a reflective layer that reflects EUV light and a protective layer that protects the reflective layer are formed in this order on the substrate,
The protective layer contains ruthenium (Ru) and at least one element selected from the group consisting of boron (B) and zirconium (Zr) as components,
The content of Ru in the protective layer is 70 at% to 95 at%, the total content of B and Zr is 5 at% to 30 at%,
A substrate with a reflective layer for EUV lithography, wherein the protective layer has an amorphous crystal structure. A substrate with a reflective layer for EUV lithography in which a reflective layer that reflects EUV light and a protective layer that protects the reflective layer are formed in this order on the substrate,
The protective layer contains Ru and at least one element selected from the group consisting of B and Zr,
The total content of B and Zr in the protective layer is such that the total content of B and Zr on the reflective layer side is high and the total content of B and Zr on the surface side is low. A gradient composition film that varies along the thickness direction of the layer,
The total content of B and Zr on the reflective layer side is 5 at% to 30 at%,
The total content of B and Zr on the surface side is 0 at% to 20 at%,
A substrate with a reflective layer for EUV lithography, wherein the protective layer has an amorphous crystal structure. The substrate with a reflective layer for EUV lithography according to claim 5 or 6, wherein the protective layer is made of any of the following solid solutions.
Solid solution of Ru and B Solid solution of Ru and Zr Solid solution of Ru, B and Zr   The protective layer comprises Ru and B as components, and the crystalline state of the protective layer maintains an amorphous state up to 200 ° C. in a vacuum (1 Pa or less). A substrate with a reflective layer for EUV lithography described in 1.   The protective layer includes Ru and Zr as components, and the crystalline state of the protective layer is maintained in an amorphous state up to 400 ° C. in a vacuum (1 Pa or less). A substrate with a reflective layer for EUV lithography described in 1.   10. The substrate with a reflective layer for EUV lithography according to claim 1, wherein the surface roughness of the protective layer surface is 0.5 nm rms or less.   The thickness of the said protective layer is 1-10 nm, The board | substrate with a reflection layer for EUV lithography in any one of the Claims 1 thru | or 10 characterized by the above-mentioned.   A reflective mask blank for EUV lithography, comprising an absorber layer formed on the protective layer of the substrate with a reflective layer for EUV lithography according to any one of claims 1 to 11.   The reflective mask blank for EUV lithography according to claim 12, wherein the absorber layer is formed of a material mainly composed of tantalum (Ta).   The reflective mask blank for EUV lithography according to claim 12 or 13, wherein an etching selectivity between the protective layer and the absorber layer is 10 or more when plasma etching is used.   15. A low reflection layer for inspection light used for inspection of a mask pattern, which is made of a material mainly composed of tantalum (Ta), is provided on the absorber layer. The reflective mask blank for EUV lithography according to any one of the above.   The contrast between the reflected light on the surface of the protective layer and the reflected light on the surface of the low reflective layer with respect to the wavelength of light used for inspection of the pattern formed on the absorber layer is 30% or more. The reflective mask blank for EUV lithography according to claim 15.   The reflective mask for EUV lithography which patterned the reflective mask blank for EUV lithography in any one of Claim 12 thru | or 16.

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